The Most Important Reason for Exploring Other Planets Is That

The most important reason for exploring other planets is that:

A) the study of the solar system is our greatest source of information on the formation of the universe.
B) it allows us to understand our own planet more thoroughly.
C) it extends human's thoughts onto a plane that is totally removed from our limited existence here on Earth.
D) it has become vital for us to develop these planets as sources of raw materials.